The concept of operating a multi-cylinder internal combustion engine on less than a total number of the cylinders available is not novel. U.S. Pat. No. 2,166,968 issued July 25, 1939 to K. W. Rohlin entitled an "Apparatus for Controlling the Operation of Internal Combustion Engines of the Multi-cylinder Type" is a rather complete thesis on the advantages of being able to operate an engine under certain operating conditions on less than the full number of cylinders available. The patent discloses the use of multiple carburetor jets arranged to deliver fuel charges to each of the cylinders independently of the other. The system includes a controlling means including a device responsive to increased speed for automatically cutting off feed of fuel to one or more of the cylinders. The disclosed system required a complex array of valves and diaphragms for controlling its operation.
During the early days of gasoline rationing in the World War II era it was proposed that fuel consumption could be decreased by permanently deactivating the intake and exhaust valves to one or more of the cylinders of the engine. It was found that the loss of horsepower resulting from the deactivation of one or more of the cylinders was not proportional to the number of cylinders that were involved. That is, if half of the cylinders were deactivated the horsepower output under all conditions of operation was substantially less than 50% resulting in poor acceleration characteristics for the vehicle. Once the change is made to the engine there is no way to switch back and forth between full cylinder and part cylinder operation without tearing down the engine and rebuilding it. A recent version of this technique is disclosed in U.S. Pat. No. 3,874,358 for an engine conversion system issued to H. D. Crower on Apr. 1, 1975.
It is an object of the present invention to provide a mechanism in which the changeover in the number of cylinders in operation automatically occurs while the engine is propelling the vehicle. In its simplest form the changeover from full power to half power and back again occurs in response to throttle position.